First measurement of the Hubble constant from a dark standard siren using the Dark Energy Survey galaxies and the LIGO/Virgo binary–black–hole merger GW170814

We present a multi–messenger measurement of the Hubble constant H₀ using the binary–black–hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the LIGO/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black–hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object–by–object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black–hole merger. Our analysis results in H₀ = 75⁺₋⁴⁰₃₂ km s⁻¹ Mpc⁻¹, which is consistent with both SN Ia and CMB measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20,140] km s⁻¹ Mpc⁻¹, and it depends on the assumed prior range. If we take a broader prior of [10,220] km s⁻¹ Mpc⁻¹, we find H₀ = 78⁺₋⁹⁶₂₄ km s⁻¹ Mpc⁻¹ (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H₀.